An X-ray CT apparatus has an X-ray tube and an X-ray detector arranged opposite each other on both sides of a test object. The X-ray detector has a plurality of channels of detecting elements along a direction perpendicular to a longer side direction of a table-top (channel direction) being a direction of a body axis of the test object.
Various types of X-ray detectors can be used for the X-ray CT apparatus. One of detectors being used for the X-ray CT apparatus in general is a scintillation detector. Elements in the scintillation detector each have a scintillator and an optical sensor such as a photodiode (PD). Further, a photon counting type X-ray CT apparatus which uses a semiconductor detector fit for photo-counting is being studied in recent years. The semiconductor detector has a semiconductor cell (X-ray detecting material) and a plurality of processing circuits formed by an ASIC layer in general.
The X-ray CT apparatus being used at present in general does not read information on detected X-ray energy, though, and is thus unable to quantitatively correct scattered radiation.
In addition, X-rays produced by the x-ray tube has energy in a broad spectrum. Thus, even if a photon counting type detector which reads information on X-ray energy is used, it cannot be distinguished whether the detected X-rays are of scattered radiation or X-rays having passed through the test object without any reaction, and no quantitative method for correcting scattered radiation has been established yet.